These Are The Most Common COVID Booster Side Effects

A third dose of the coronavirus vaccine could cause symptoms on par with previous shots. Here's what to expect.
The side effects of a booster vaccine aren't expected to be too different than what people experienced with their initial vaccinations.
Teresa Colucci via Getty Images
The side effects of a booster vaccine aren't expected to be too different than what people experienced with their initial vaccinations.

COVID booster shots are officially here for some people. The Food and Drug Administration recently authorized a third dose of the Pfizer vaccine for those who are 65 and older. It was also authorized for anyone between the ages of 18 and 64 who is considered to be at high risk of becoming severely ill, as well as those whose jobs increase their risk of serious disease (like healthcare workers). Individuals who are immunocompromised have been authorized to get a third dose as well.

Those who are eligible might be wondering: What will the experience be like this time? Will I feel the same way I did when I first rolled up my sleeves?

Here’s what we know about the most common booster side effects so far:

Redness And Swelling

Experts are still gathering information about the potential side effects of a third shot. The Centers for Disease Control and Prevention is continually sorting through data to look for patterns and to detect new or unusual adverse events.

But data Pfizer submitted to federal officials in its request for emergency use authorization of a third dose, shows the main side effects have been very much in line with what we’ve seen with the first and second doses. The top side effect in its trial was pain at the injection site.

“There’s about 5% more pain at the injection site, but the vast majority of that is mild pain,” said Dean Blumberg, a pediatric infectious diseases specialist with UC Davis Health. He noted that the data available to experts so far is coming largely from pre-print data (not yet subject to peer review) or information presented at Advisory Committee on Immunization Practices meetings.

If you have a sore arm, the CDC suggests applying a cool, wet washcloth to the area. You should also continue to use and exercise or move your arm.


Fatigue was the second-most-common side effect in Pfizer’s booster application; it was also a common side effect for earlier doses of coronavirus mRNA vaccinations

“It’s very similar to the second dose,” Blumberg said.

He added, however, that there’s no way to know whether people who were really exhausted after the second shot would experience something similar after a third dose, or if they’d have a milder reaction — or vice versa.

The first dose of the mRNA vaccines basically introduces your body to SARS-CoV-2; the second dose gets your immune system to recognize the spike protein and mount an antibody response, which can lead to more intense symptoms as your body does what it’s supposed to do.

In a press release accompanying its bid for emergency use authorization, Pfizer stated that the frequency of side effects was “similar to or better than” what people experienced after their second shots.

Muscle And Joint Pain

Muscle pain and joint pain are among the most common side effects experienced after the initial doses, and that’s likely to be the case again with booster shots.

But in general it’s not recommended to take over-the-counter medicines like ibuprofen, acetaminophen or aspirin before vaccination with the hopes of preventing side effects, because it may lessen the body’s immune response to the vaccine. (Still, experts have said that if you happen to take one of those medications beforehand, it’s probably fine, with one expert previously telling HuffPost the advice is “boringly conservative.” Just don’t go out of your way to do it if you don’t have to.)

Fever Or Chills

Fever and chills are another common side effect of the COVID-19 vaccines — and likely the booster dose as well.

Again, it’s reasonable to plan as though you might experience symptoms like you did after the Johnson & Johnson vaccine or the second dose of either of the two mRNA vaccines.

“Be prepared. If you get a third dose, you don’t want to have something really important planned the next day, like a birthday party, or a really important presentation at work, or a test if you’re a student,” Blumberg said. “I’d plan on being prepared for some reactions in the day or two following that third dose.”

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.

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